Plant pests are a major factor in the loss of the world's important agricultural crops. About $8 billion is lost every year in the U.S. due to infestations of plants by non-mammalian pests including insects. In addition to losses in field crops, insect pests are also a burden to vegetable and fruit growers, to producers of ornamental flowers, and to home gardeners. For example, pest thrips such as Frankliniella occidentalis and Thrips tabaci cause extensive damage to horticultural crops such as salad vegetables, cut flowers and ornamental plants, resulting in significant economic loss to the growers.
Insect pests are mainly controlled by intensive applications of chemical pesticides, which are active through inhibition of insect growth, prevention of insect feeding or reproduction, or cause death. Although the use of such chemicals can result in good control of insect pests, the widespread use of chemical pesticides can result in the appearance of resistant insect varieties. Further, high levels of chemicals on horticultural crops, in particular salad vegetables, are undesirable to many consumers.
Therefore, an alternative method of pest control involving the use of beneficial insects or mites has been developed. The beneficial insects or mites are predatory towards pest insects such as thrips, and can be applied to crops to control insect pests. Beneficial insects or mites can be provided to crop plants in a variety of ways, for example manually or through a controlled release device. The use of beneficial insects or mites forms part of integrated crop management and integrated pest management programs, combining cultural, biological and chemical means to achieve sustainable pest control.
One example of a beneficial insect or mite system is the use of Amblyseius cucumeris as a predatory mite for the control of pest thrips. Existing systems involve the mite being provided either loose in bran and vermiculite for sprinkling onto crops, or in sachets for longer periods of protection. Amblyseius cucumeris feed on first instar thrips larvae, and control relies on complete cover of a crop with the predator before thrips establish. Repeated sprinkling of the predator over crops is labor intensive, wasteful and messy as much of the bran falls on the floor or gets stuck on the leaves. Establishment on crops is relatively slow, and therefore the existing sachet products were designed as an improved method of release.
The existing sachet products provide a continuous release of Amblyseius cucumeris for several weeks by maintaining a breeding population of the mite with a food source in the form of a grain mite (Tyrophagus spp.). The mites are contained in a bran matrix, with or without vermiculite. The breeding colony is maintained in a sachet with a hook attached to the sachet for placement onto plants, or onto wires used to support the crop. Mites emerge from the sachet onto the crop through a small perforation in the sachet, the emergence hole or aperture.
Although an improvement over previous systems, there are still several problems with the existing sachet products. In some growing systems, water or nutrient solutions are provided to plants through overhead irrigation systems, usually mist or sprinkler systems. In other growing systems, crops are grown under shade netting and natural rainfall wets the crop. In existing sachets, water can enter the sachet such that the contents become wet, the mites then cease to breed, and the sachet life is therefore reduced considerably. For example, water enters the sachet through the emergence aperture. Also, water collects on the seals on the outside of the sachet and is drawn into the sachet through capillary action along paper fibers. Another problem with existing sachets is that the hook becomes wet, distorts, and allows the sachet to fall to the ground. Further problems with existing sachets include a variable rate of release of beneficial mites, and a low overall release rate. This is a particular problem in wet conditions.
Therefore, there is a long-felt need in the art for an improved system for the delivery of beneficial insects or mites to cropping environments. The presently disclosed subject matter describes a new system for providing beneficial insects or mites, which overcomes these problems.